Dynamic simulation and safety evaluation of high-speed trains meeting in open air

Dynamic responses of a carriage under excitation with the German high-speed low-interference track spectrum together with the air pressure pulse generated as high-speed trains passing each other are investigated with a multi-body dynamics method.The variations of degrees of freedom(DOFs:horizontal movement,roll angle,and yaw angle),the lateral wheel-rail force,the derailment coefficient and the rate of wheel load reduction with time when two carriages meet in open air are obtained and compared with the results of a single train travelling at specifie speeds.Results show that the rate of wheel load reduction increases with the increase of train speed and meets some safety standard at a certain speed,but exceeding the value of the rate of wheel load reduction does not necessarily mean derailment.The evaluation standard of the rate of wheel load reduction is somewhat conservative and may be loosened.The pressure pulse has significan effects on the train DOFs,and the evaluations of these safety indexes are strongly suggested in practice.The pressure pulse has a limited effect on the derailment coefficien and the lateral wheel-rail force,and,thus,their further evaluations may be not necessary.     

Investigation of aerodynamic effects on the high-speed train exposed to longitudinal and lateral wind velocities

The wind stability of the high-speed train has gained an increasing interest in the last few years. In this paper, an investigation of the effects of stochastic winds with longitudinal and lateral components on the high-speed train is described. The longitudinal and lateral wind time histories at the position of a moving vehicle, for a variety of wind directions, are first simulated. An algorithm for computing the unsteady aerodynamic load time histories is then derived for a moving vehicle. A typical railway vehicle has been modeled using the vehicle dynamic simulation package ‘Simpack’, and the unsteady wind loads of the same vehicle are applied to the vehicle model to investigate the dynamic response behavior. The simulated vehicle behavior is assessed against the indicator of load reduction factor, which indicates wheel unloading and therefore potential roll over. The characteristic wind curves (CWC) and its spread range are then obtained to evaluate the operational safety of the high-speed train. The results demonstrate that the operational safety of the high-speed train will be overestimated if the lateral wind velocity is not considered, especially for the small angles between vehicle and wind.